Field of the Invention
The invention relates to a pump drive unit for conveying a process fluid as described herein.
Background of the Invention
Pump drive units in which a pump having an impeller and a drive for the pump are surrounded by a common housing are frequently used for applications in which the pump is entirely or completely immersed in a liquid, e.g. water, or when the pump is operated at locations with difficult access or under difficult conditions or environmental conditions.
One application example for this is represented by pumps which are used for fluidized bed processes or ebullated bed processes in the hydrocarbon processing industry. These processes serve, for example, to purify heavy hydrocarbons, e.g. heavy fuel oil, or to purify refinery residues or to break them down into more easily usable, more highly volatile hydrocarbons. This is frequently done by applying hydrogen to the heavy hydrocarbons, wherein the mixed components are swirled in a reactor and the heavy hydrocarbons are there broken down with the aid of catalysts. To circulate the process fluid, which typically very largely comprises heavy hydrocarbons, in an ebullated bed reactor or fluidized bed reactor, special pump drive units are used for which the name ebullating pump has become common. These ebullating pumps are as a rule provided directly at the reactor as circulation pumps for the process fluid and are configured for process reasons such that the pump is arranged above the drive with respect to the vertical. Ebullating pumps have to work as reliably as possible and over a long time period in permanent operation under extremely challenging conditions.